1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of manufacturing the same.
2. Description of the Related Art
There is known a liquid crystal display device having a structure in which a plate-shaped component such as a surface plate or a touch panel is bonded onto a liquid crystal display panel. For the bonding, a UV-curable adhesive is used. In this method, a thickness distribution of the UV adhesive deteriorates due to the influence of warpage and deformation of the plate-shaped component and the liquid crystal display panel and the parallelism of the bonded devices. Accordingly, a difference occurs in shrinkage amount in the course of cure, and due to the action thereof, a stress is applied to the liquid crystal display panel to cause display unevenness. As a countermeasure, it is conceivable to alleviate the stress by increasing the thickness of the UV adhesive, but there is a problem that the UV adhesive flows out from a bonded end surface because of the fluidity of the UV adhesive after bonding. Further, in the case of bonding a surface plate subjected to printing in a frame shape, a difference occurs in degree of cure of the UV adhesive because of a difference in light amount of UV light between a printing portion and a transparent portion. Similarly to the above, a liquid crystal display panel substrate is deformed due to a difference in stress applied to the liquid crystal display panel to cause display unevenness.
As a countermeasure, there has been devised a bonding process that uses a double-sided pressure sensitive adhesive sheet which eliminates the thickness difference at a bonded portion and does not need a cure process. However, an adhered member is adhered by the double-sided pressure sensitive adhesive sheet and hence cannot be moved after bonding. Accordingly, there has been a drawback that highly-accurate bonding needs an expensive device provided with an alignment mechanism. Further, in the case where a sheet having no base material is used as the double-sided pressure sensitive adhesive sheet, the cohesion force is high and hence it is difficult to peel off the sheet after bonding. Accordingly, there has been another drawback that the reparability such as the reuse of a component in the process is significantly deteriorated. As means for solving the problems, there has been devised a liquid crystal display device which uses a double-sided pressure sensitive adhesive sheet in which a PET sheet is provided as a base material and adhesives are provided on both surfaces thereof (Japanese Patent Application Laid-open No. 2009-229538).
In the above-mentioned method, the base material is present in the pressure sensitive adhesive sheet, and hence air bubbles are apt to be generated due to a step at a frame-shaped printing portion formed on a surface plate. Accordingly, it has been necessary, to reduce a printing step or increase the thickness of the pressure sensitive adhesive layer, which requires a wide range of restrictions.